1. Field of the Invention
The present invention relates to an image display, and more particularly, it relates to an image display providing different images or the like to observers located on different observational positions.
2. Cross-Reference to Related Applications
The priority application No. JP2005-76203 upon which this patent application is based is hereby incorporated by reference.
3. Description of the Background Art
A stereoscopic image display displaying three-dimensional stereoscopic images and a two-screen display presenting different images to observers positioned on different observational positions are known in general. Further, a parallax barrier system is generally proposed as a technique for the stereoscopic image display displaying three-dimensional stereoscopic images, as disclosed in Japanese Patent No. 2857429, for example. The aforementioned Japanese Patent No. 2857429 discloses a three-dimensional image display capable of forming openings and shields of prescribed shapes on prescribed positions of an electronic parallax barrier arranged on the side of an image display surface closer to an observer in the form of stripes by controlling the electronic parallax barrier with control means such as a microcomputer. In order to provide three-dimensional images to the observer, the three-dimensional image display disclosed in Japanese Patent No. 2857429 forms the openings of the electronic parallax barrier to introduce left- and right-eye images into the left and right eyes of the observer respectively. In order to provide two-dimensional (planar) images to the observer, on the other hand, the three-dimensional image display introduces all images into both eyes of the observer by controlling the electronic parallax barrier to open the overall area thereof.
A two-screen display capable of presenting different images to observers located on different observational positions by arranging a barrier provided with slitlike openings and shields on the side of a display panel closer to the observers is also proposed in general. FIG. 26 is a plan view for illustrating the principle of an exemplary conventional two-screen display 500. The structure of the conventional two-screen display 500 according to a barrier system is now described with reference to FIG. 26.
As shown in FIG. 26, the conventional two-screen display 500 according to the barrier system comprises a display panel 501 for displaying images, a polarizing plate 502 arranged on a side of the display panel 501 closer to observers 510 and 520 and a barrier 503 provided on a side of the polarizing plate 502 closer to the observes 510 and 520.
The display panel 501 is alternately provided with pixel trains 501a and 501b extending in a direction (perpendicular to the plane of FIG. 26) substantially perpendicular to a line segment connecting left and right eyes 510a and 510b (520a and 520b) of the observer 510 (520) with each other. The display panel 501 is also provided with a glass substrate 501c of glass (refractive index n1=about 1.53) having a thickness A (about 0.5 mm). The display 500 displays images L1 and R1 to be observed by the observers 510 and 520 on the pixel trains 501a and 501b respectively. The pixel trains 501a and 501b are at a pixel pitch B (about 0.06 mm). The polarizing plate 502 of resin (refractive index n2=about 1.49) has a thickness C (about 0.1 mm).
The barrier 503 is provided with shields 503a and openings 503b for blocking and transmitting light received from the display panel 501 respectively. The shields 503a and the openings 503b extend in the direction (perpendicular to the plane of FIG. 26) substantially perpendicular to the line segment connecting the left and right eyes 510a and 510b (520a and 520b) of the observer 510 (520) with each other, similarly to the pixel trains 501a and 501b of the display panel 501. The shields 503a and the openings 503b are provided in correspondence to sets of the pixel trains 501a and 501b of the display panel 501 respectively. The barrier 503 has a function of limiting the angle of light emitted from the pixel trains 501a and 501b of the display panel 501 with the shields 503a thereof.
A two-screen display method according to the conventional two-screen display 500 is now described with reference to FIG. 26.
When observing the display panel 501 of the conventional two-screen display 500 through the openings 503b of the barrier 503 from a position separated from the display panel 501 by an observational distance D (about 600 mm), the observer 510 observes the images L1 displayed on the pixel trains 501a of the display panel 501. When observing the display panel 501 through the openings 503b of the barrier 503 from another position separated from the display panel 501 by the observational distance D (about 600 mm), the observer 520 observes the images R1 displayed on the pixel trains 501b of the display panel 501. Thus, the observers 510 and 520 located on different observational positions can observe different images in an observational range E respectively.
In the conventional two-screen display 500 shown in FIG. 26, the observational range E of the observers 510 and 520 satisfies the following expression (1) through similarity between triangles 550 and 560:D:(C/n2)+(A/n1)=E:B  (1)This expression (1) is transformed into the following expression (2) for obtaining the observational range E:E=(B×D)/{(C/n2)+(A/(n1))  (2)It is understood from this expression (2) that the observational range E is proportional to (dependent upon) the pixel pitch B of the display panel 501. When the values B=0.06 mm, D=600 mm, C=0.1 mm, A=0.5 mm, n1=1.53 and n2=1.49 are substituted in the above expression (2), the observational range E is equal to 91.4 (mm). In other words, the observational range E of the observers 510 and 520 is about 91.4 mm (9.14 cm) in the conventional two-screen display 500 shown in FIG. 26 employing the display panel 501 having the pixel pitch B (about 0.06 mm).
In the conventional two-screen display 500 shown in FIG. 26, however, the observational range E proportional to (dependent upon) the pixel pitch B of the display panel 501 is disadvantageously reduced if the pixel pitch B is reduced. If the pixel pitch B of the display panel 501 is smaller than 0.06 mm, for example, the observational range E of the observers 510 and 520 is also smaller than 9.14 cm, and hence it is difficult for the observers 510 and 520 to observe the images L1 and R1. In the conventional two-screen display 500 shown in FIG. 26, therefore, it is difficult to employ a high-definition display panel having a small pixel pitch. Consequently, it is difficult to provide high-definition images to the observers 510 and 520 located on different observational positions.
Further, the shields 503a of the barrier 503 disadvantageously partially block the light received from the display panel 501 since the barrier 503 is arranged on the side of the display panel 501 closer to the observers 510 and 520. Consequently, the images L1 and R1 observed by the observers 510 and 520 disadvantageously appear dark due to reduction of brightness thereof.
In the three-dimensional image display disclosed in the aforementioned Japanese Patent No. 2857429, the shields of the electronic parallax barrier arranged on the side of the image display surface closer to the observer disadvantageously partially block light emitted from an image display surface. Consequently, the images observed by the observer disadvantageously appear dark due to reduction of brightness thereof.